The invention relates to a hot regenerator for use in a cryogenic refrigerator of the type described in the patent to Vuilleumier, U.S. Pat. No. 1,275,507. Various internal and external hot regenerators have been used with cryogenic refrigerators using the Vuilleumier cycle. The regenerator is a matrix having a high ratio of surface area to volume. One type of prior art regenerator uses a fine mesh screen. These have been found to result in excessive hot regenerator losses. The gas path between the hot displacer and the hot cylinder wall has been used as a regenerator path. However, nonuniform gas flow paths produce regenerator losses and it has been very difficult to maintain a uniform gas flow path between the hot displacer and hot cylinder.